Reflection is the change in direction (position) of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated.
Refraction is the change in direction (position) of a wave due to a change in its speed. This is most generally observed when a wave passes from one medium to another medium at an angle.
Reflection of light is either diffuse (retaining the energy, but losing the image) or specular (mirror-like) depending on the nature of the interface. Furthermore, if the interface is between a conductor and a dielectric, the phase of the reflected wave is retained; otherwise if the interface is between two dielectrics, the phase may be inverted or retained, depending on the indices of refraction.
Types of reflection:
- Diffuse reflection
- Complex conjugate reflection
- Neutron reflection
- Sound reflection
- Seismic reflection
Laws of reflection:
The laws of reflection are as follows:
- The incident and the reflected ray and then normal to the reflection surface at the point of the incidence lie in the same plane.
- The angle which the incident ray (i) makes with the normal is equal to the given angle which the reflected ray makes to the same normal.
- Light paths are reversible.
Refraction of light is the most generally observed phenomenon, but any type of wave can refract when it interacts with a medium, for example when sound waves pass from one medium into another or when water waves move into water of a different depth.
Refraction is described by Using Snell’s law, which states that the angle of incidence θ1 is related to the angle of refraction θ2 by
Sin θ1/sinθ2 = v1/v2 = n2/n1
Here v1 and v2 are the wave velocities in the respective media, and n1 and n2 the refractive indices.